1. Field of the Invention
The present invention relates to a constitution in the case where lamp annealing is utilized as a heating treatment method frequently used in a fabrication process of a semiconductor device. Particularly, the present invention is effective in fabricating a semiconductor device such as a thin film transistor (TFT) on a glass substrate.
2. Description of Related Art
In recent years, development of TFT formed by utilizing a semiconductor thin film (typically thin film whose major component is silicon) on a glass substrate has significantly been progressed. Further, demand of an electrooptical device in which a pixel matrix circuit, a driver circuit, a logic circuit and the like are monolithically mounted on a glass substrate has been promoted.
The most significant restriction caused in forming TFT on a glass substrate is temperature of process. That is, a restriction whereby a heating treatment cannot be carried out at a heat resistant temperature of glass or higher narrows the margin of process.
Therefore, laser annealing process has been utilized as a means for annealing selectively a thin film. According to the laser annealing process, only a thin film can selectively be heated by elevating instantaneously temperature of a sample by irradiating a pulse laser beam onto the sample. However, there has been posed a problem in view of mass production steps in which an optical system is complicated to deal with a laser beam and the uniformity is difficult to ensure.
Hence, a lamp annealing process using a strong beam emitted from an arc lamp, a halogen lamp or the like has recently been spotlighted. This technology is referred to as RTA (Rapid Thermal Annealing) or RTP (Rapid Thermal Processing) in which a film to be treated is heated by irradiating a strong beam in a region of wavelength that is apt to be absorbed by the film to be treated.
Normally, the lamp annealing process utilizes a region of visible light to infrared light as strong beam. The light in this wavelength region is difficult to absorb by a glass substrate and accordingly, the heating of the glass substrate can be restrained to a minimum. Further, time periods for temperature rise and temperature drop are extremely short and accordingly, high temperature treatment at 1000xc2x0 C. or higher can be carried out in a short period of time of several seconds to several tens seconds.
Further, a complicated optical system such as used in a fabrication process by using a laser beam is not needed and therefore, the process is suitable for treating a comparatively large area with excellent uniformity. Also, the yield and throughput are promoted since the high temperature treatment is basically carried out by a sheet by sheet process.
It is a problem of the present invention to improve the above-described lamp annealing process and to provide a method for effectively subjecting a film to be treated to a heating treatment.
Further, according to the conventional lamp annealing process, light has been irradiated only from an upper face side of a film to be treated and therefore, when a layer which does not transmit the light (for example, electrode made of a metal) or a layer which hinders irradiation of light is present at a portion or a total face of the film to be treated, the film to be treated beneath the layer could not be annealed.
Particularly, when the conventional lamp annealing process was used in a step of activating impurities doped in a semiconductor thin film, an electrode made of a metal and an insulating film which were laminated on the semiconductor thin film hindered irradiation of light and source/drain regions excellent in uniformity could not be formed.
It is one of the problems of the present invention to provide a semiconductor thin film having source/drain regions excellent in uniformity by activating impurities through a step using a heating treatment method improving the conventional lamp annealing process in a semiconductor thin film doped with impurities and by heat treatment at later steps.
According to a first aspect of the present invention disclosed in the specification, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source,
wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation is irradiated from an upper face side of the thin film and simultaneously therewith a strong light in a wavelength region capable of subjecting the bonds to a vibrational excitation is irradiated from a lower face side of the thin film.
In the first aspect of the present invention, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is a light included in a wavelength region of 10 through 600 nm; and
the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is a light included in a wavelength region of 500 nm through 20 xcexcm.
In the first aspect of the present invention, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is an ultraviolet light, and
the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is an infrared light.
Further, according to a second aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source,
wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation is irradiated from an upper face side of the thin film and simultaneously therewith a strong light in a wavelength region capable of subjecting the bonds to a vibrational excitation is irradiated from a lower face side of the thin film, and
wherein the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.
According to a third aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source:
wherein a strong light in a wavelength region capable of subjecting bonds of atoms constituting the thin film to an electron excitation and a strong light in a wavelength capable of subjecting the bonds to the vibrational excitation are irradiated from an upper face side of the thin film and simultaneously therewith a strong light in the wavelength capable of subjecting the bonds to the vibrational excitation is irradiated from a lower face side of the thin film; and
wherein the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.
In the third aspect of the present invention, an infrared light irradiated from the upper face side of the thin film is irradiated to regions of the thin film immediately before and/or immediately after a region of the thin film where an ultraviolet light is irradiated.
In the second aspect or the third aspect of the present invention, all of the strong light in the wavelength region capable of subjecting the bonds to the electron excitation and the strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are scanned in a state of irradiating a same portion of the thin film.
In the second aspect or the third aspect of the present invention, a first region where the strong lights in the wavelength region capable of subjecting the bonds to the vibrational excitation are irradiated includes a second region where the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is irradiated and is wider than the second region.
In the above-described aspects, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is a light included in a wavelength region of 10 through 600 nm, and
the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is a light included in a wavelength region of 500 nm through 20 xcexcm.
In the above-described aspects, the strong light in the wavelength region capable of subjecting the bonds to the electron excitation is an ultraviolet light, and
the strong light in the wavelength region capable of subjecting the bonds to the vibrational excitation is an infrared light.
Further, according to a fourth aspect of the present invention, there is provided a heating treatment method which is a method of subjecting a thin film formed on a substrate having a light transmitting performance to a heating treatment by using a lamp light source, said method comprising the steps of,
subjecting bonds of atoms constituting the thin film to an electron excitation by irradiating an ultraviolet light from an upper face side of the thin film,
subjecting the bonds to a vibrational excitation by irradiating an infrared light from a lower face side of the thin film, and
wherein the step of subjecting the thin film to the electron excitation and the step of subjecting the thin film to the vibrational excitation are carried out simultaneously.
Additionally, in carrying out the present invention comprising the above-described aspects, there is needed a heating treatment device comprising at least,
an ultraviolet light lamp arranged on an upper face side of a substrate to be treated,
an infrared light lamp arranged on a lower face side of the substrate to be treated, and
wherein the ultraviolet light lamp and the infrared light lamp are arranged to interpose the substrate to be treated.
Further, in carrying out the above-described aspects of the present invention, there is needed a heating treatment device comprising at least,
an ultraviolet light lamp and an infrared light lamp arranged on an upper face side of a substrate to be treated;
an infrared light lamp arranged on a lower face side of the substrate to be treated, and
wherein the ultraviolet light lamp and the infrared light lamps are arranged to interpose the substrate to be treated.
In the above-described aspects of the heating treatment device, the infrared light lamp arranged on the upper face side of the substrate to be treated is an auxiliary lamp for irradiating a region different from a region irradiated by the ultraviolet light lamp.
Further, according to the inventors, the most preferable constitution of the present invention is a constitution where infrared light and ultraviolet light are fabricated in a linear shape and irradiated. In that cases a heating treatment device in which an ultraviolet light lamp and an infrared light lamp are in a rod-like shape or a cylindrical shape having a longitudinal direction in a direction in parallel with a substrate to be treated may be used. Further, it is effective to also arrange cylindrical lenses between the ultraviolet light lamp and the substrate to be treated and between the infrared light lamp and the substrate to be treated.
Further, according to a fifth aspect of the present invention, there is provided a method of fabricating a semiconductor device for subjecting a semiconductor thin film formed on a substrate having a light transmitting performance to a heating treatment by irradiating a strong light, said method comprising the steps of,
irradiating strong beams emitted from at least one lamp light source provided on an upper face side of the semiconductor thin film and at least one lamp light source provided on a lower face side of the semiconductor thin film to the semiconductor thin film, and
carrying out a heat treatment on the semiconductor thin film after the step of irradiating the strong beams.
According to a sixth aspect of the present invention, there is provided a method of fabricating a semiconductor device for irradiating a semiconductor thin film doped with impurities and subjecting the semiconductor thin film to a heating treatment thereby activating the impurities, said method comprising the steps of,
irradiating strong lights emitted from at least one lamp light source provided on an upper face side of the semiconductor thin film and at least one lamp light source provided on a lower face side of the semiconductor thin film to the semiconductor thin film, and
carrying out a heat treatment on the semiconductor thin film after the step of irradiating the strong beams.
In the fifth aspect or the sixth aspect of the present invention, the heat treatment is carried out by a furnace annealing process at 500 through 700xc2x0 C.
In the fifth aspect or the sixth aspect of the present invention, strain energy of the semiconductor thin film is reduced by the heat treatment.
In the fifth aspect or the sixth aspect of the present invention, the strong lights are scanned from one end to other end of the substrate in a state of being fabricated in a linear shape.
In the fifth aspect or the sixth aspect of the present invention, all of the strong lights are scanned in a state of irradiating a same portion of the thin film.
In the fifth aspect or the sixth aspect of the present invention, the strong light from the upper face side is a light whose major component is in a wavelength region capable of subjecting bonds of atoms of the semiconductor thin film to an electron excitation, and
the strong beam from the lower face side is a light whose major component is in a wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to a vibrational excitation.
Further, in the above-described aspects of the present invention, the strong light in the wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to the electron excitation is an ultraviolet light, and
the strong light in the wavelength region capable of subjecting the bonds of the atoms of the thin film to the vibrational excitation is an infrared light.
Further, in the above-described aspects of the present invention, the wavelength region capable of subjecting the bonds of the atoms of the semiconductor thin film to the electron excitation falls in a range of 10 through 600 nm, and
the wavelength region capable of subjecting the bonds of the atoms of the thin film to the vibrational excitation falls in a range of 500 nm through 20 xcexcm.